Thefirst test of a fission bomb released an amount of energy approximately equal to 20,000tons of TNT (84 TJ).[1] The first thermonuclear ("hydrogen") bombtest released energy approximately equal to 10 million tons of TNT (42 PJ). Nuclear bombs have hadyields between 10 tons TNT (theW54) and 50 megatons for theTsar Bomba (seeTNT equivalent). A thermonuclear weapon weighing as little as 600 pounds (270 kg) can release energy equal to more than 1.2 megatonnes of TNT (5.0 PJ) (this is nearly the record for the ratio between yield and weapon weight, achieved with theW56).[2]
TheTrinity test of theManhattan Project was the first detonation of a nuclear weapon, which ledJ. Robert Oppenheimer to recall verses from theHindu scriptureBhagavad Gita: "If the radiance of a thousand suns were to burst at once into the sky, that would be like the splendor of the mighty one "... "I am become Death, the destroyer of worlds".[9]J. Robert Oppenheimer, principal leader of theManhattan Project, often referred to as the "father of the atomic bomb".
There are two basic types of nuclear weapons: those that derive the majority of their energy fromnuclear fission reactions alone, and those that use fission reactions to beginnuclear fusion reactions that produce a large amount of the total energy output.[10]
All existing nuclear weapons derive some of their explosive energy from nuclear fission reactions. Weapons whose explosive output is exclusively from fission reactions are commonly referred to asatomic bombs oratom bombs (abbreviated asA-bombs). This has long been noted as something of amisnomer, as their energy comes from thenucleus of the atom, just as it does with fusion weapons.
In fission weapons, a mass offissile material (enriched uranium orplutonium) is forced intosupercriticality—allowing anexponential growth ofnuclear chain reactions—either by shooting one piece of sub-critical material into another (the "gun" method) or by compression of a sub-critical sphere or cylinder of fissile material using chemically fueledexplosive lenses. The latter approach, the "implosion" method, is more sophisticated and more efficient (smaller, less massive, and requiring less of the expensive fissile fuel) than the former.
A major challenge in all nuclear weapon designs is to ensure that a significant fraction of the fuel is consumed before the weapon destroys itself. The amount of energy released by fission bombs can range from the equivalent of just under a ton to upwards of 500,000 tons (500kilotons) ofTNT (4.2 to 2.1×106 GJ).[11]
All fission reactions generatefission products, the remains of the split atomic nuclei. Many fission products are either highlyradioactive (but short-lived) or moderately radioactive (but long-lived), and as such, they are a serious form ofradioactive contamination. Fission products are the principal radioactive component ofnuclear fallout. Another source of radioactivity is the burst of free neutrons produced by the weapon. When they collide with other nuclei in the surrounding material, the neutrons transmute those nuclei into other isotopes, altering their stability and making them radioactive.
The most commonly used fissile materials for nuclear weapons applications have beenuranium-235 andplutonium-239. Less commonly used has beenuranium-233.Neptunium-237 and some isotopes ofamericium may be usable for nuclear explosives as well, but it is not clear that this has ever been implemented, and their plausible use in nuclear weapons is a matter of dispute.[12]
The basics of theTeller–Ulam design for a hydrogen bomb: a fission bomb uses radiation to compress and heat a separate section of fusion fuel.
The other basic type of nuclear weapon produces a large proportion of its energy in nuclear fusion reactions. Such fusion weapons are generally referred to asthermonuclear weapons or more colloquially ashydrogen bombs (abbreviated asH-bombs), as they rely on fusion reactions between isotopes ofhydrogen (deuterium andtritium). All such weapons derive a significant portion of their energy from fission reactions used to "trigger" fusion reactions, and fusion reactions can themselves trigger additional fission reactions.[13]
Only six countries—theUnited States,Russia, theUnited Kingdom,China,France, andIndia—have conducted thermonuclear weapon tests. Whether India has detonated a "true" multi-stagedthermonuclear weapon is controversial.[14]North Korea claims to have tested a fusion weapon as of January 2016[update], though this claim is disputed.[15] Thermonuclear weapons are considered much more difficult to successfully design and execute than primitive fission weapons. Almost all of the nuclear weapons deployed today use the thermonuclear design because it results in an explosion hundreds of times stronger than that of a fission bomb of similar weight.[16]
Thermonuclear bombs work by using the energy of a fission bomb to compress and heat fusion fuel. In theTeller-Ulam design, which accounts for all multi-megaton yield hydrogen bombs, this is accomplished by placing a fission bomb and fusion fuel (tritium,deuterium, orlithium deuteride) in proximity within a special, radiation-reflecting container. When the fission bomb is detonated,gamma rays andX-rays emitted first compress the fusion fuel, then heat it to thermonuclear temperatures. The ensuing fusion reaction creates enormous numbers of high-speedneutrons, which can then induce fission in materials not normally prone to it, such asdepleted uranium. Each of these components is known as a "stage", with the fission bomb as the "primary" and the fusion capsule as the "secondary". In large, megaton-range hydrogen bombs, about half of the yield comes from the final fissioning of depleted uranium.[11]
Virtually all thermonuclear weapons deployed today use the "two-stage" design described to the right, but it is possible to add additional fusion stages—each stage igniting a larger amount of fusion fuel in the next stage. This technique can be used to construct thermonuclear weapons of arbitrarily large yield. This is in contrast to fission bombs, which are limited in their explosive power due tocriticality danger (premature nuclear chain reaction caused by too-large amounts of pre-assembled fissile fuel). The largest nuclear weapon ever detonated, theTsar Bomba of the USSR, which released an energy equivalent of over 50 megatons of TNT (210 PJ), was a three-stage weapon. Most thermonuclear weapons are considerably smaller than this, due to practical constraints from missile warhead space and weight requirements.[17] In the early 1950s theLivermore Laboratory in the United States had plans for the testing of two massive bombs, Gnomon andSundial, 1 gigaton of TNT and 10 gigatons of TNT respectively.[18][19]
Edward Teller, often referred to as the "father of the hydrogen bomb"
Fusion reactions do not create fission products, and thus contribute far less to the creation ofnuclear fallout than fission reactions, but because allthermonuclear weapons contain at least onefission stage, and many high-yield thermonuclear devices have a final fission stage, thermonuclear weapons can generate at least as much nuclear fallout as fission-only weapons. Furthermore, high yield thermonuclear explosions (most dangerously ground bursts) have the force to lift radioactive debris upwards past thetropopause into thestratosphere, where the calm non-turbulent winds permit the debris to travel great distances from the burst, eventually settling and unpredictably contaminating areas far removed from the target of the explosion.
There are other types of nuclear weapons as well. For example, aboosted fission weapon is a fission bomb that increases its explosive yield through a small number of fusion reactions, but it is not a fusion bomb. In the boosted bomb, the neutrons produced by the fusion reactions serve primarily to increase the efficiency of the fission bomb. There are two types of boosted fission bomb: internally boosted, in which a deuterium-tritium mixture is injected into the bomb core, and externally boosted, in which concentric shells of lithium-deuteride and depleted uranium are layered on the outside of the fission bomb core. The external method of boosting enabled theUSSR to field the first partially thermonuclear weapons, but it is now obsolete because it demands a spherical bomb geometry, which was adequate during the 1950s arms race when bomber aircraft were the only available delivery vehicles.
The detonation of any nuclear weapon is accompanied by a blast ofneutron radiation. Surrounding a nuclear weapon with suitable materials (such ascobalt orgold) creates a weapon known as asalted bomb. This device can produce exceptionally large quantities of long-livedradioactive contamination. It has been conjectured that such a device could serve as a "doomsday weapon" because such a large quantity of radioactivities with half-lives of decades, lifted into the stratosphere where winds would distribute it around the globe, would make all life on the planet extinct.
In connection with theStrategic Defense Initiative, research into thenuclear pumped laser was conducted under the DOD programProject Excalibur but this did not result in a working weapon. The concept involves the tapping of the energy of an exploding nuclear bomb to power a single-shot laser that is directed at a distant target.
During theStarfish Prime high-altitude nuclear test in 1962, an unexpected effect was produced which is called anuclear electromagnetic pulse. This is an intense flash of electromagnetic energy produced by a rain of high-energy electrons which in turn are produced by a nuclear bomb's gamma rays. This flash of energy can permanently destroy or disrupt electronic equipment if insufficiently shielded. It has been proposed to use this effect to disable an enemy's military and civilian infrastructure as an adjunct to other nuclear or conventional military operations. By itself it could as well be useful to terrorists for crippling a nation's economic electronics-based infrastructure. Because the effect is most effectively produced by high altitude nuclear detonations (by military weapons delivered by air, though ground bursts also produce EMP effects over a localized area), it can produce damage to electronics over a wide, even continental, geographical area.[20]
Research has been done into the possibility ofpure fusion bombs: nuclear weapons that consist of fusion reactions without requiring a fission bomb to initiate them. Such a device might provide a simpler path to thermonuclear weapons than one that required the development of fission weapons first, and pure fusion weapons would create significantly less nuclear fallout than other thermonuclear weapons because they would not disperse fission products. In 1998, theUnited States Department of Energy divulged that the United States had, "...made a substantial investment" in the past to develop pure fusion weapons, but that, "The U.S. does not have and is not developing a pure fusion weapon", and that, "No credible design for a pure fusion weapon resulted from the DOE investment".[21]
Nuclear isomers provide a possible pathway to fissionless fusion bombs. These are naturally occurringisotopes (178m2Hf being a prominent example) which exist in an elevated energy state. Mechanisms to release this energy as bursts of gamma radiation (as in thehafnium controversy) have been proposed as possible triggers for conventional thermonuclear reactions.
Antimatter, which consists ofparticles resembling ordinarymatter particles in most of their properties but having oppositeelectric charge, has been considered as a trigger mechanism for nuclear weapons.[22][23][24] A major obstacle is the difficulty of producing antimatter in large enough quantities, and there is no evidence that it is feasible beyond the military domain.[25] However, the US Air Force funded studies of the physics of antimatter in theCold War, and began considering its possible use in weapons, not just as a trigger, but as the explosive itself.[26] A fourth generation nuclear weapon design[22] is related to, and relies upon, the same principle asantimatter-catalyzed nuclear pulse propulsion.[27]
SovietOTR-21 Tochka missile. Capable of firing a 100-kiloton nuclear warhead a distance of 185 km
Some nuclear weapons are designed for special purposes; most of these are for non-strategic (decisively war-winning) purposes and are referred to astactical nuclear weapons.
Theneutron bomb purportedly conceived bySam Cohen is a thermonuclear weapon that yields a relatively small explosion but a relatively large amount of neutronradiation. Such a weapon could, according to tacticians, be used to cause massive biological casualties while leaving inanimate infrastructure mostly intact and creating minimal fallout. Because high energy neutrons are capable of penetrating dense matter, such as tank armor, neutron warheads were procured in the 1980s (though not deployed in Europe) for use as tactical payloads for US Army artillery shells (200 mmW79 and 155 mmW82) andshort range missile forces. Soviet authorities announced similar intentions for neutron warhead deployment in Europe; indeed, they claimed to have originally invented the neutron bomb, but their deployment on USSR tactical nuclear forces is unverifiable.[citation needed]
A type of nuclear explosive most suitable for use by ground special forces was theSpecial Atomic Demolition Munition, or SADM, sometimes popularly known as asuitcase nuke. This is a nuclear bomb that is man-portable, or at least truck-portable, and though of a relatively small yield (one or two kilotons) is sufficient to destroy important tactical targets such as bridges, dams, tunnels, important military or commercial installations, etc. either behind enemy lines or pre-emptively on friendly territory soon to be overtaken by invading enemy forces. These weapons require plutonium fuel and are particularly "dirty". They also demand especially stringent security precautions in their storage and deployment.[citation needed]
Small "tactical" nuclear weapons were deployed for use as antiaircraft weapons. Examples include the USAFAIR-2 Genie, theAIM-26 Falcon and US ArmyNike Hercules. Missile interceptors such as theSprint and theSpartan also used small nuclear warheads (optimized to produce neutron or X-ray flux) but were for use against enemy strategic warheads.[citation needed]
Other small, or tactical, nuclear weapons were deployed by naval forces for use primarily asantisubmarine weapons. These included nucleardepth bombs or nuclear armed torpedoes. Nuclear mines for use on land or at sea are also possibilities.[citation needed]
The first nuclear weapons weregravity bombs, such as this "Fat Man" weapon dropped onNagasaki, Japan. They were large and could only be delivered byheavy bomber aircraftA demilitarized,commercial launch of the RussianStrategic Rocket Forces R-36ICBM; also known by the NATO reporting name:SS-18 Satan. Upon its first fielding in the late 1960s, the SS-18 remains the single highestthrow weight missile delivery system ever built.
The system used todeliver a nuclear weapon to its target is an important factor affecting bothnuclear weapon design andnuclear strategy. The design, development, and maintenance of delivery systems are among the most expensive parts of a nuclear weapons program; they account, for example, for 57% of the financial resources spent by the United States on nuclear weapons projects since 1940.[28]
The simplest method for delivering a nuclear weapon is agravity bomb dropped fromaircraft; this was the method used by theUnited States against Japan in 1945. This method places few restrictions on the size of the weapon. It does, however, limit attack range, response time to an impending attack, and the number of weapons that a country can field at the same time. With miniaturization, nuclear bombs can be delivered by bothstrategic bombers and tacticalfighter-bombers. This method is the primary means of nuclear weapons delivery; the majority of US nuclear warheads, for example, are free-fall gravity bombs, namely theB61, which is being improved upon to this day.[11][29]
Preferable from a strategic point of view is a nuclear weapon mounted on amissile, which can use aballistic trajectory to deliver the warhead over the horizon. Although even short-range missiles allow for a faster and less vulnerable attack, the development of long-rangeintercontinental ballistic missiles (ICBMs) andsubmarine-launched ballistic missiles (SLBMs) has given some nations the ability to plausibly deliver missiles anywhere on the globe with a high likelihood of success.
More advanced systems, such asmultiple independently targetable reentry vehicles (MIRVs), can launch multiple warheads at different targets from one missile, reducing the chance of a successfulmissile defense. Today, missiles are most common among systems designed for delivery of nuclear weapons. Making a warhead small enough to fit onto a missile, though, can be difficult.[11]
Nuclear warfare strategy is a set of policies that deal with preventing or fighting a nuclear war. The policy of trying to prevent an attack by a nuclear weapon from another country by threatening nuclear retaliation is known as the strategy ofnuclear deterrence. The goal in deterrence is to always maintain a second strike capability (the ability of a country to respond to a nuclear attack with one of its own) and potentially to strive forfirst strike status (the ability to destroy an enemy's nuclear forces before they could retaliate). During the Cold War, policy and military theorists considered the sorts of policies that might prevent a nuclear attack, and they developedgame theory models that could lead to stable deterrence conditions.[30]
The now decommissioned United States'Peacekeeper missile was anICBM developed to replace theMinuteman missile in the late 1980s. Each missile, like theheavier lift RussianSS-18 Satan, could contain up to ten nuclear warheads (shown in red), each of which could be aimed at a different target. A factor in the development ofMIRVs was to make completemissile defense difficult for an enemy country.
Different forms ofnuclear weapons delivery (see above) allow for different types of nuclear strategies. The goals of any strategy are generally to make it difficult for an enemy to launch a pre-emptive strike against the weapon system and difficult to defend against the delivery of the weapon during a potential conflict. This can mean keeping weapon locations hidden, such as deploying them onsubmarines or land mobiletransporter erector launchers whose locations are difficult to track, or it can mean protecting weapons by burying them in hardenedmissile silo bunkers. Other components of nuclear strategies included using missile defenses to destroy the missiles before they land or implementingcivil defense measures using early-warning systems to evacuate citizens to safe areas before an attack.
Weapons designed to threaten large populations or to deter attacks are known asstrategic weapons. Nuclear weapons for use on abattlefield in military situations are calledtactical weapons.
Critics of nuclear war strategy often suggest that a nuclear war between two nations would result in mutual annihilation. From this point of view, the significance of nuclear weapons is to deter war because any nuclear war would escalate out of mutual distrust and fear, resulting inmutually assured destruction. This threat of national, if not global, destruction has been a strong motivation for anti-nuclear weapons activism.
Critics from the peace movement and within the military establishment[citation needed] have questioned the usefulness of such weapons in the current military climate. According to anadvisory opinion issued by theInternational Court of Justice in 1996, the use of (or threat of use of) such weapons would generally be contrary to the rules of international law applicable in armed conflict, but the court did not reach an opinion as to whether or not the threat or use would be lawful in specific extreme circumstances such as if the survival of the state were at stake.
Ballistic missile submarines have been of great strategic importance for the United States, Russia, and other nuclear powers since they entered service in theCold War, as they can hide fromreconnaissance satellites and fire their nuclear weapons with virtual impunity.
Anotherdeterrence position is thatnuclear proliferation can be desirable. In this case, it is argued that, unlike conventional weapons, nuclear weapons deter all-out war between states, and they succeeded in doing this during theCold War between the US and theSoviet Union.[31] In the late 1950s and early 1960s, Gen.Pierre Marie Gallois of France, an adviser toCharles de Gaulle, argued in books likeThe Balance of Terror: Strategy for the Nuclear Age (1961) that mere possession of a nuclear arsenal was enough to ensure deterrence, and thus concluded that the spread of nuclear weapons could increaseinternational stability. Some prominentneo-realist scholars, such asKenneth Waltz andJohn Mearsheimer, have argued, along the lines of Gallois, that some forms of nuclear proliferation would decrease the likelihood oftotal war, especially in troubled regions of the world where there exists a single nuclear-weapon state. Aside from the public opinion that opposes proliferation in any form, there are two schools of thought on the matter: those, like Mearsheimer, who favored selective proliferation,[32] and Waltz, who was somewhat more non-interventionist.[33][34] Interest in proliferation and thestability-instability paradox that it generates continues to this day, with ongoing debate about indigenous Japanese andSouth Korean nuclear deterrent againstNorth Korea.[35]
The threat of potentially suicidal terrorists possessing nuclear weapons (a form ofnuclear terrorism) complicates the decision process. The prospect ofmutually assured destruction might not deter an enemy who expects to die in the confrontation. Further, if the initial act is from a statelessterrorist instead of a sovereign nation, there might not be a nation or specific target to retaliate against. It has been argued, especially after theSeptember 11, 2001, attacks, that this complication calls for a new nuclear strategy, one that is distinct from that which gave relative stability during the Cold War.[36] Since 1996, the United States has had a policy of allowing the targeting of its nuclear weapons at terrorists armed withweapons of mass destruction.[37]
Robert Gallucci argues that although traditional deterrence is not an effective approach toward terrorist groups bent on causing a nuclear catastrophe, Gallucci believes that "the United States should instead consider a policy of expanded deterrence, which focuses not solely on the would-be nuclear terrorists but on those states that may deliberately transfer or inadvertently leak nuclear weapons and materials to them. By threatening retaliation against those states, the United States may be able to deter that which it cannot physically prevent.".[38]
Graham Allison makes a similar case, arguing that the key to expanded deterrence is coming up with ways of tracing nuclear material to the country that forged the fissile material. "After a nuclear bomb detonates,nuclear forensics cops would collect debris samples and send them to a laboratory for radiological analysis. By identifying unique attributes of the fissile material, including its impurities and contaminants, one could trace the path back to its origin."[39] The process is analogous to identifying a criminal by fingerprints. "The goal would be twofold: first, to deter leaders of nuclear states from selling weapons to terrorists by holding them accountable for any use of their weapons; second, to give leaders every incentive to tightly secure their nuclear weapons and materials."[39]
According to the Pentagon's June 2019 "Doctrine for Joint Nuclear Operations" of the Joint Chiefs of Staffs website Publication, "Integration of nuclear weapons employment with conventional and special operations forces is essential to the success of any mission or operation."[40][41]
TheInternational Atomic Energy Agency was created in 1957 to encourage peaceful development of nuclear technology while providing international safeguards against nuclear proliferation.
Because they are weapons of mass destruction, the proliferation and possible use of nuclear weapons are important issues in international relations and diplomacy. In most countries, the use of nuclear force can only be authorized by thehead of government orhead of state.[c] Despite controls and regulations governing nuclear weapons, there is an inherent danger of "accidents, mistakes, false alarms, blackmail, theft, and sabotage".[42]
In the late 1940s, lack of mutual trust prevented the United States and the Soviet Union from making progress on arms control agreements. TheRussell–Einstein Manifesto was issued inLondon on July 9, 1955, byBertrand Russell in the midst of the Cold War. It highlighted the dangers posed by nuclear weapons and called for world leaders to seek peaceful resolutions to international conflict. The signatories included eleven pre-eminent intellectuals and scientists, includingAlbert Einstein, who signed it just days before his death on April 18, 1955. A few days after the release, philanthropistCyrus S. Eaton offered to sponsor a conference—called for in the manifesto—inPugwash, Nova Scotia, Eaton's birthplace. This conference was to be the first of thePugwash Conferences on Science and World Affairs, held in July 1957.
By the 1960s, steps were taken to limit both the proliferation of nuclear weapons to other countries and the environmental effects ofnuclear testing. ThePartial Nuclear Test Ban Treaty (1963) restricted all nuclear testing tounderground nuclear testing, to prevent contamination from nuclear fallout, whereas theTreaty on the Non-Proliferation of Nuclear Weapons (1968) attempted to place restrictions on the types of activities signatories could participate in, with the goal of allowing the transference of non-militarynuclear technology to member countries without fear of proliferation.
In 1957, theInternational Atomic Energy Agency (IAEA) was established under the mandate of theUnited Nations to encourage development of peaceful applications of nuclear technology, provide international safeguards against its misuse, and facilitate the application of safety measures in its use. In 1996, many nations signed theComprehensive Nuclear-Test-Ban Treaty,[43] which prohibits all testing of nuclear weapons. A testing ban imposes a significant hindrance to nuclear arms development by any complying country.[44] The Treaty requires the ratification by 44 specific states before it can go into force; as of 2012[update], the ratification of eight of these states is still required.[43]
Additional treaties and agreements have governed nuclear weapons stockpiles between the countries with the two largest stockpiles, the United States and the Soviet Union, and later between the United States and Russia. These include treaties such asSALT II (never ratified),START I (expired),INF,START II (never in effect),SORT, andNew START, as well as non-binding agreements such asSALT I and the Presidential Nuclear Initiatives[45] of 1991. Even when they did not enter into force, these agreements helped limit and later reduce the numbers and types of nuclear weapons between the United States and the Soviet Union/Russia.
Nuclear weapons have also been opposed by agreements between countries. Many nations have been declaredNuclear-Weapon-Free Zones, areas where nuclear weapons production and deployment are prohibited, through the use of treaties. TheTreaty of Tlatelolco (1967) prohibited any production or deployment of nuclear weapons inLatin America and theCaribbean, and theTreaty of Pelindaba (1964) prohibits nuclear weapons in many African countries. As recently as 2006 aCentral Asian Nuclear Weapon Free Zone was established among the former Soviet republics of Central Asia prohibiting nuclear weapons.
Additionally, there have been other, specific actions meant to discourage countries from developing nuclear arms. In the wake of the tests by India and Pakistan in 1998, economic sanctions were (temporarily) levied against both countries, though neither were signatories with the Nuclear Non-Proliferation Treaty. One of the statedcasus belli for the initiation of the 2003Iraq War was an accusation by the United States that Iraq was actively pursuing nuclear arms (though this was soon discoverednot to be the case as the program had been discontinued). In 1981, Israel hadbombed a nuclear reactor being constructed inOsirak,Iraq, in what it called an attempt to halt Iraq's previous nuclear arms ambitions; in 2007, Israelbombed another reactor being constructed inSyria.
In 2013,Mark Diesendorf said that governments of France, India, North Korea, Pakistan, UK, and South Africa have used nuclear power or research reactors to assist nuclear weapons development or to contribute to their supplies of nuclear explosives from military reactors.[47] In 2017, 122 countries mainly in theGlobal South voted in favor of adopting theTreaty on the Prohibition of Nuclear Weapons, which eventually entered into force in 2021.[48]
TheDoomsday Clock measures the likelihood of a human-madeglobal catastrophe and is published annually by theBulletin of the Atomic Scientists. The two years with the highest likelihood had previously been 1953, when the Clock was set to two minutes until midnight after the US and the Soviet Union began testing hydrogen bombs, and 2018, following the failure of world leaders to address tensions relating to nuclear weapons and climate change issues.[49] In 2023, following theescalation of nuclear threats during theRussian invasion of Ukraine, the doomsday clock was set to 90 seconds, the highest likelihood of global catastrophe since the existence of the Doomsday Clock.[50]
As of 2024, Russia has intensified nuclear threats in Ukraine and is reportedly planning to place nuclear weapons in orbit, breaching the 1967 Outer Space Treaty. China is significantly expanding its nuclear arsenal, with projections of over 1,000 warheads by 2030 and up to 1,500 by 2035. North Korea is progressing in intercontinental ballistic missile tests and has a mutual-defense treaty with Russia, exchanging artillery for possible missile technology. Iran is currently viewed as a nuclear "threshold" state.[51]
TheUSSR and United States nuclear weapon stockpiles throughout theCold War until 2015, with a precipitous drop in total numbers following the end of the Cold War in 1991.
Nuclear disarmament refers to both the act of reducing or eliminating nuclear weapons and to the end state of a nuclear-free world, in which nuclear weapons are eliminated.
Beginning with the 1963Partial Test Ban Treaty and continuing through the 1996Comprehensive Nuclear-Test-Ban Treaty, there have been many treaties to limit or reduce nuclear weapons testing and stockpiles. The 1968Nuclear Non-Proliferation Treaty has as one of its explicit conditions that all signatories must "pursue negotiations in good faith" towards the long-term goal of "complete disarmament". The nuclear-weapon states have largely treated that aspect of the agreement as "decorative" and without force.[52]
Only one country—South Africa—has ever fully renounced nuclear weapons they had independently developed. The former Soviet republics ofBelarus,Kazakhstan, andUkraine returned Soviet nuclear arms stationed in their countries to Russia after thecollapse of the USSR.
Proponents of nuclear disarmament say that it would lessen the probability of nuclear war, especially accidentally. Critics of nuclear disarmament say that it would undermine the presentnuclear peace and deterrence and would lead to increased global instability. Various American elder statesmen,[53] who were in office during theCold War period, have been advocating the elimination of nuclear weapons. These officials includeHenry Kissinger,George Shultz,Sam Nunn, andWilliam Perry. In January 2010,Lawrence M. Krauss stated that "no issue carries more importance to the long-term health and security of humanity than the effort to reduce, and perhaps one day, rid the world of nuclear weapons".[54]
Ukrainian workers use equipment provided by the USDefense Threat Reduction Agency to dismantle a Soviet-era missile silo. After the end of the Cold War, Ukraine and the other non-Russian, post-Soviet republics relinquished Soviet nuclear stockpiles to Russia.
In January 1986, Soviet leaderMikhail Gorbachev publicly proposed a three-stage program for abolishing the world's nuclear weapons by the end of the 20th century.[55] In the years after the end of the Cold War, there have been numerous campaigns to urge the abolition of nuclear weapons, such as that organized by theGlobal Zero movement, and the goal of a "world without nuclear weapons" was advocated by United States PresidentBarack Obama in an April 2009 speech inPrague.[56] ACNN poll from April 2010 indicated that the American public was nearly evenly split on the issue.[57]
Some analysts have argued that nuclear weapons have made the world relatively safer, with peace throughdeterrence and through thestability–instability paradox, including in south Asia.[58][59]Kenneth Waltz has argued that nuclear weapons have helped keep an uneasy peace, and further nuclear weapon proliferation might even help avoid the large scale conventional wars that were so common before their invention at the end ofWorld War II.[34] But former SecretaryHenry Kissinger says there is a new danger, which cannot be addressed by deterrence: "The classical notion of deterrence was that there was some consequences before which aggressors and evildoers would recoil. In a world of suicide bombers, that calculation doesn't operate in any comparable way".[60]George Shultz has said, "If you think of the people who are doing suicide attacks, and people like that get a nuclear weapon, they are almost by definition not deterrable".[61]
As of early 2019, more than 90% of world's 13,865 nuclear weapons were owned by Russia and the United States.[62][63]
Its goal is to promote nuclear disarmament andnon-proliferation and the strengthening of the disarmament regimes in respect to other weapons of mass destruction,chemical andbiological weapons. It also promotes disarmament efforts in the area ofconventional weapons, especiallyland mines andsmall arms, which are often the weapons of choice in contemporary conflicts.
Even before the first nuclear weapons had been developed, scientists involved with theManhattan Project were divided over the use of the weapon. The role of the two atomic bombings of the country inJapan's surrender and the US'sethical justification for them has been the subject of scholarly and popular debate for decades. The question of whether nations should have nuclear weapons, or test them, has been continually and nearly universally controversial.[65]
May 21, 1946: While conducting further experiments on the same core at Los Alamos National Laboratory, physicistLouis Slotin accidentally caused the core to become brieflysupercritical. He received a lethal dose ofgamma andneutron radiation, and died nine days later on May 30, 1946. After the death of Daghlian and Slotin, the mass became known as the "demon core". It was ultimately used to construct a bomb for use on the Nevada Test Range.[67]
February 13, 1950: aConvair B-36B crashed in northernBritish Columbia after jettisoning aMark IV atomic bomb. This was the first suchnuclear weapon loss in history. The accident was designated a "Broken Arrow"—an accident involving a nuclear weapon, but which does not present a risk of war. Experts believe that up to 50 nuclear weapons were lost during the Cold War.[68]
May 22, 1957: a 42,000-pound (19,000 kg)Mark-17 hydrogen bomb accidentally fell from a bomber near Albuquerque, New Mexico. The detonation of the device's conventional explosives destroyed it on impact and formed a crater 25 feet (7.6 m) in diameter on land owned by theUniversity of New Mexico. According to a researcher at the Natural Resources Defense Council, it was one of the most powerful bombs made to date.[69]
January 17, 1966: the1966 Palomares B-52 crash occurred when aB-52G bomber of theUSAF collided with aKC-135 tanker duringmid-air refuelling off the coast ofSpain. The KC-135 was completely destroyed when its fuel load ignited, killing all four crew members. The B-52G broke apart, killing three of the seven crew members aboard.[74] Of the fourMk28 typehydrogen bombs the B-52G carried,[75] three were found on land nearAlmería, Spain. The non-nuclear explosives in two of the weapons detonated upon impact with the ground, resulting in the contamination of a 2-square-kilometer (490-acre) (0.78 square mile) area byradioactiveplutonium. The fourth, which fell into theMediterranean Sea, was recovered intact after a 21⁄2-month-long search.[76]
September 18–19, 1980: theDamascus Accident occurred in Damascus, Arkansas, where aTitan Missile equipped with a nuclear warhead exploded. The accident was caused by a maintenance man who dropped a socket from a socket wrench down an 80-foot (24 m) shaft, puncturing a fuel tank on the rocket. Leaking fuel resulted in ahypergolic fuel explosion, jettisoning theW-53 warhead beyond the launch site.[79][80][81]
Over 2,000 nuclear explosions have been conducted in over a dozen different sites around the world. Red Russia/Soviet Union, blue France, light blue United States, violet Britain, yellow China, orange India, brown Pakistan, green North Korea and light green (territories exposed to nuclear bombs). The black dot indicates the location of theVela incident.This view of downtownLas Vegas shows amushroom cloud in the background. Scenes such as this were typical during the 1950s. From 1951 to 1962 the government conducted 100 atmospheric tests at the nearbyNevada Test Site.
Over 500 atmospheric nuclear weapons tests were conducted at various sites around the world from 1945 to 1980.Radioactive fallout from nuclear weapons testing was first drawn to public attention in 1954 when theCastle Bravo hydrogen bomb test at thePacific Proving Grounds contaminated the crew and catch of the Japanese fishing boatLucky Dragon.[82] One of the fishermen died in Japan seven months later, and the fear of contaminatedtuna led to a temporary boycotting of the popular staple in Japan. The incident caused widespread concern around the world, especially regarding the effects of nuclear fallout and atmosphericnuclear testing, and "provided a decisive impetus for the emergence of the anti-nuclear weapons movement in many countries".[82]
As public awareness and concern mounted over the possible health hazards associated with exposure to the nuclear fallout, various studies were done to assess the extent of the hazard. ACenters for Disease Control and Prevention/National Cancer Institute study claims that fallout from atmospheric nuclear tests would lead to perhaps 11,000 excess deaths among people alive during atmospheric testing in the United States from all forms of cancer, including leukemia, from 1951 to well into the 21st century.[83][84]As of March 2009[update], the US is the only nation that compensates nuclear test victims. Since theRadiation Exposure Compensation Act of 1990, more than $1.38 billion in compensation has been approved. The money is going to people who took part in the tests, notably at theNevada Test Site, and to others exposed to the radiation.[85][86]
In addition, leakage of byproducts of nuclear weapon production into groundwater has been an ongoing issue, particularly at theHanford site.[87]
A photograph ofSumiteru Taniguchi's back injuries taken in January 1946 by a US Marine photographer
Some scientists estimate that a nuclear war with 100 Hiroshima-size nuclear explosions on cities could cost the lives of tens of millions of people from long-term climatic effects alone. The climatology hypothesis is thatif each cityfirestorms, a great deal of soot could be thrown up into the atmosphere which could blanket the earth, cutting out sunlight for years on end, causing the disruption of food chains, in what is termed anuclear winter.[88][89]
People near the Hiroshima explosion and who managed to survive the explosion subsequently suffered a variety of horrible medical effects. Some of these effects are still present to this day:[90]
Initial stage—the first 1–9 weeks, in which are the greatest number of deaths, with 90% due to thermal injury or blast effects and 10% due to super-lethalradiation exposure.
Intermediate stage—from 10 to 12 weeks. The deaths in this period are fromionizing radiation in the median lethal range –LD50
Late period—lasting from 13 to 20 weeks. This period has some improvement in survivors' condition.
Delayed period—from 20+ weeks. Characterized by numerous complications, mostly related to healing of thermal and mechanical injuries, and if the individual was exposed to a few hundred to a thousandmillisieverts of radiation, it is coupled with infertility, sub-fertility and blood disorders. Furthermore, ionizing radiation above a dose of around 50–100 millisievert exposure has been shown to statistically begin increasing one's chance of dying of cancer sometime in their lifetime over the normal unexposed rate of ~25%, in the long term, a heightened rate of cancer, proportional to the dose received, would begin to be observed after ~5+ years, with lesser problems such as eyecataracts and other more minor effects in other organs and tissue also being observed over the long term.
Fallout exposure—depending on if further afield individualsshelter in place or evacuate perpendicular to the direction of the wind, and therefore avoid contact with the fallout plume, and stay there for the days and weeks after the nuclear explosion, their exposure to fallout, and therefore their total dose, will vary. With those who do shelter in place, and or evacuate, experiencing a total dose that would be negligible in comparison to someone who just went about their life as normal.[91][92]
Staying indoors until after the most hazardous falloutisotope,I-131 decays away to 0.1% of its initial quantity after tenhalf-lifes—which is represented by 80 days inI-131s case, would make the difference between likely contractingThyroid cancer or escaping completely from this substance depending on the actions of the individual.[93]
Mushroom cloud from the explosion ofCastle Bravo, the largest nuclear weapon detonated by the US, in 1954
Nuclear war could yield unprecedented human death tolls andhabitat destruction. Detonating large numbers of nuclear weapons would have an immediate, short term and long-term effects on the climate, potentially causing cold weather known as a "nuclear winter".[94][95] In 1982,Brian Martin estimated that aUS–Soviet nuclear exchange might kill 400–450 million directly, mostly in the United States, Europe and Russia, and maybe several hundred million more through follow-up consequences in those same areas.[96] Many scholars have posited that a global thermonuclear war with Cold War-era stockpiles, or even with the current smaller stockpiles, may lead to theextinction of the human race.[97] TheInternational Physicians for the Prevention of Nuclear War believe that nuclear war could indirectly contribute to human extinction via secondary effects, including environmental consequences,societal breakdown, and economic collapse. It has been estimated that a relatively small-scale nuclear exchange betweenIndia and Pakistan involving 100Hiroshima yield (15 kilotons) weapons, could cause a nuclear winter and kill more than a billion people.[98]
According to a peer-reviewed study published in the journalNature Food in August 2022, a full-scale nuclear war between the US and Russia would directly kill 360 million people and more than 5 billion people would die fromstarvation. More than 2 billion people could die from a smaller-scale nuclear war between India and Pakistan.[95][99][100]
Protest in Bonn against thenuclear arms race between the US/NATO and the Warsaw Pact, 1981Demonstration against nuclear testing inLyon, France, in the 1980s
Peace movements emerged in Japan and in 1954 they converged to form a unified "Japan Council against Atomic and Hydrogen Bombs." Japanese opposition to nuclear weapons tests in the Pacific Ocean was widespread, and "an estimated 35 million signatures were collected on petitions calling for bans on nuclear weapons".[101]
In 1959, a letter in theBulletin of the Atomic Scientists was the start of a successful campaign to stop theAtomic Energy Commission dumpingradioactive waste in the sea 19 kilometres fromBoston.[104] In 1962,Linus Pauling won theNobel Peace Prize for his work to stop the atmospheric testing of nuclear weapons, and the "Ban the Bomb" movement spread.[65]
In 1963, many countries ratified thePartial Test Ban Treaty prohibiting atmospheric nuclear testing. Radioactive fallout became less of an issue and the anti-nuclear weapons movement went into decline for some years.[82][105] A resurgence of interest occurred amid European and Americanfears of nuclear war in the 1980s.[106]
According to an audit by theBrookings Institution, between 1940 and 1996, the US spent $11.7 trillion in present-day terms[107] on nuclear weapons programs. 57% of which was spent on buildingnuclear weapons delivery systems. 6.3% of the total$, 732 billion in present-day terms, was spent onenvironmental remediation andnuclear waste management, for example cleaning up theHanford site, and 7% of the total$, 820 billion was spent on making nuclear weapons themselves.[108]
Peaceful nuclear explosions arenuclear explosions conducted for non-military purposes, such as activities related toeconomic development including the creation ofcanals. During the 1960s and 1970s, both the United States and the Soviet Union conducted a number of PNEs.[109] The United States created plans for several uses of PNEs, includingOperation Plowshare.[110] Six of the explosions by the Soviet Union are considered to have been of an applied nature, not just tests.
The United States and the Soviet Union later halted their programs. Definitions and limits are covered in the Peaceful Nuclear Explosions Treaty of 1976.[111][112] The stalledComprehensive Nuclear-Test-Ban Treaty of 1996 would prohibit all nuclear explosions, regardless of whether they are for peaceful purposes or not.[113]
Innuclear fission, the nucleus of a fissile atom (in this case,enriched uranium) absorbs a thermal neutron, becomes unstable and splits into two new atoms, releasing some energy and between one and three new neutrons, which can perpetuate the process.
In the first decades of the 20th century,physics was revolutionized with developments in the understanding of the nature ofatoms including the discoveries inatomic theory byJohn Dalton.[114] Around the turn of the 20th century, it was discovered byHans Geiger andErnest Marsden and thenErnest Rutherford, that atoms had a highly dense, very small, charged central core called an atomic nucleus. In 1898,Pierre andMarie Curie discovered thatpitchblende, an ore ofuranium, contained a substance—which they namedradium—that emitted large amounts ofradiation. Ernest Rutherford andFrederick Soddy identified that atoms were breaking down and turning into different elements. Hopes were raised among scientists and laymen that the elements around us could contain tremendous amounts of unseen energy, waiting to be harnessed.
In December 1938,Otto Hahn andFritz Strassmann reported that they had detected the elementbarium after bombarding uranium with neutrons.Lise Meitner andOtto Robert Frisch correctly interpreted these results as being due to the splitting of the uranium atom. Frisch confirmed this experimentally on January 13, 1939.[115] They gave the process the name "fission" because of its similarity to thesplitting of a cell into two new cells. Even before it was published, news of Meitner's and Frisch's interpretation crossed the Atlantic.[116] In their second publication on nuclear fission in February 1939, Hahn and Strassmann predicted the existence and liberation of additional neutrons during the fission process, opening up the possibility of anuclear chain reaction.
Leo Szilard, pictured in about 1960, invented the electron microscope, linear accelerator, cyclotron, nuclear chain reaction and patented the nuclear reactor
After learning about the German fission in 1939,Leo Szilard concluded thaturanium would be the element which can realize his 1933 idea about nuclear chain reaction.[117]
Uranium appears in nature primarily in two isotopes:uranium-238 anduranium-235. When the nucleus of uranium-235 absorbs a neutron, it undergoes nuclear fission, releasing energy and, on average, 2.5 neutrons. Because uranium-235 releases more neutrons than it absorbs, it can support a chain reaction and so is described asfissile. Uranium-238, on the other hand, is not fissile as it does not normally undergo fission when it absorbs a neutron.
By the start of the war in September 1939, many scientists likely to be persecuted by the Nazis had already escaped. Physicists on both sides were well aware of the possibility of utilizing nuclear fission as a weapon, but no one was quite sure how it could be engineered. In August 1939, concerned that Germany might haveits own project to develop fission-based weapons,Albert Einstein signeda letter to U.S. President Franklin D. Roosevelt warning him of the threat.[118]
Roosevelt responded by setting up theUranium Committee underLyman James Briggs but, with little initial funding ($6,000), progress was slow. It was not until the U.S. entered the war in December 1941 that Washington decided to commit the necessary resources to a top-secret high priority bomb project.[119]
Organized research first began in Britain and Canada as part of theTube Alloys project: the world's first nuclear weapons project. TheMaud Committee was set up following the work of Frisch andRudolf Peierls who calculated uranium-235's critical mass and found it to be much smaller than previously thought which meant that a deliverable bomb should be possible.[120] In the February 1940Frisch–Peierls memorandum they stated that: "The energy liberated in the explosion of such a super-bomb...will, for an instant, produce a temperature comparable to that of the interior of the sun. The blast from such an explosion would destroy life in a wide area. The size of this area is difficult to estimate, but it will probably cover the centre of a big city."
Edgar Sengier, a director ofShinkolobwe Mine in the Congo which produced by far the highest quality uranium ore in the world, had become aware of uranium's possible use in a bomb. In late 1940, fearing that it might be seized by the Germans, he shipped the mine's entire stockpile of ore to a warehouse in New York.[121]
The final iteration of theGadget nuclear device prior to its successful test on July 16, 1945, the culmination of the United States' 3-yearManhattan Project's research and development of nuclear weapons
^In the United States, the President and the Secretary of Defense, acting as theNational Command Authority, mustjointly authorize the use of nuclear weapons.
^Executive release."South African nuclear bomb".Nuclear Threat Initiatives. Nuclear Threat Initiatives, South Africa (NTI South Africa). Archived fromthe original on September 28, 2012. RetrievedMarch 13, 2012.
^Educational Foundation for Nuclear Science, Inc. (February 1954)."Bulletin of the Atomic Scientists".Bulletin of the Atomic Scientists: Science and Public Affairs. Educational Foundation for Nuclear Science, Inc.: 61–.ISSN0096-3402.Archived from the original on March 31, 2017.
^Gsponer, Andre; Hurni, Jean-Pierre (1987). "The physics of antimatter induced fusion and thermonuclear explosions". In Velarde, G.; Minguez, E. (eds.).Proceedings of the 4th International Conference on Emerging Nuclear Energy Systems, Madrid, June 30/July 4, 1986. World Scientific, Singapore. pp. 166–169.arXiv:physics/0507114.
^Gallucci, Robert (September 2006). "Averting Nuclear Catastrophe: Contemplating Extreme Responses to U.S. Vulnerability".Annals of the American Academy of Political and Social Science.607:51–58.doi:10.1177/0002716206290457.S2CID68857650.
^abPreparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (2010). "Status of Signature and RatificationArchived April 6, 2011, at theWayback Machine". Accessed May 27, 2010. Of the "Annex 2" states whose ratification of the CTBT is required before it enters into force, China, Egypt, Iran, Israel, and the United States have signed but not ratified the Treaty. India, North Korea, and Pakistan have not signed the Treaty.
^Richelson, Jeffrey.Spying on the bomb: American nuclear intelligence from Nazi Germany to Iran and North Korea. New York: Norton, 2006.
^"Ticonderoga Cruise Reports". Archived fromthe original(Navy.mil weblist of Aug 2003 compilation from cruise reports) on September 7, 2004. RetrievedApril 20, 2012.The National Archives hold[s] deck logs for aircraft carriers for the Vietnam Conflict.
^Christ, Mark K."Titan II Missile Explosion".The Encyclopedia of Arkansas History & Culture. Arkansas Historic Preservation Program.Archived from the original on September 12, 2014. RetrievedAugust 31, 2014.
^Stumpf, David K. (2000). Christ, Mark K.; Slater, Cathryn H. (eds.)."We Can Neither Confirm Nor Deny" Sentinels of History: Refelections on Arkansas Properties on the National Register of Historic Places. Fayetteville, Arkansas: University of Arkansas Press.
^"Decay Information".Fallout Radiation.com.Archived from the original on August 31, 2011.7 hour rule: At 7 hours after detonation the fission product activity will have decreased to about 1/10 (10%) of its amount at 1 hour. At about 2 days (49 hours-7X7) the activity will have decreased to 1% of the 1-hour value
DeVolpi, Alexander, Minkov, Vladimir E., Simonenko, Vadim A., and Stanford, George S.Nuclear Shadowboxing: Contemporary Threats from Cold War Weaponry. Fidlar Doubleday, 2004 (Two volumes, both accessible on Google Book Search) (Content of both volumes is now available in the 2009 trilogy by Alexander DeVolpi:Nuclear Insights: The Cold War Legacy)
(in French) Jean-Hugues Oppel,Réveillez le président, Éditions Payot et rivages, 2007 (ISBN978-2-7436-1630-4). The book is a fiction about thenuclear weapons of France; the book also contains about ten chapters on true historical incidents involving nuclear weapons and strategy.
Laura Grego and David Wright, "Broken Shield: Missiles designed to destroy incoming nuclear warheads fail frequently in tests and could increase global risk of mass destruction",Scientific American, vol. 320, no. no. 6 (June 2019), pp. 62–67. "Current U.S.missile defense plans are being driven largely bytechnology,politics andfear. Missile defenses will not allow us to escape our vulnerability to nuclear weapons. Instead large-scale developments will create barriers to taking real steps towardreducing nuclear risks—by blocking further cuts in nuclear arsenals and potentially spurring new deployments." (p. 67.)
Moniz, Ernest J., andSam Nunn, "The Return of Doomsday: The New Nuclear Arms Race – and How Washington and Moscow Can Stop It",Foreign Affairs, vol. 98, no. 5 (September / October 2019), pp. 150–161. FormerU.S. Secretary of EnergyErnest Moniz and formerU.S. SenatorSam Nunn write that "the old [strategic] equilibrium" between the United States and Russia has been "destabilized" by "clashing national interests, insufficient dialogue, eroding arms control structures, advanced missile systems, and newcyberweapons... Unless Washington and Moscow confront these problems now, a major international conflict or nuclear escalation is disturbingly plausible—perhaps even likely." (p. 161.)
Tom Stevenson, "A Tiny Sun" (review ofFred Kaplan,The Bomb: Presidents, Generals, and the Secret History of Nuclear War, Simon and Schuster, 2021, 384 pp.; and Keir A. Lieber and Daryl G. Press,The Myth of the Nuclear Revolution: Power Politics in the Atomic Age, Cornell, 2020, 180 pp.),London Review of Books, vol. 44, no. 4 (24 February 2022), pp. 29–32. "Nuclear strategists systematically underestimate the chances of nuclear accident... [T]here have been too many close calls for accidental use to be discounted." (p. 32.)
David Wright and Cameron Tracy, "Over-hyped: Physics dictates thathypersonic weapons cannot live up to the grand promises made on their behalf",Scientific American, vol. 325, no. 2 (August 2021), pp. 64–71. "Failure to fully assess [the potential benefits and costs of hypersonic weapons] is a recipe for wasteful spending and increased global risk." (p. 71.)
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